Klotho is a recently-discovered anti-aging gene. Genetic mutation of klotho results in multiple premature aging phenotypes. In contrast, mice that overexpress klotho enjoy an extended lifespan. Thus, klotho may be an aging-suppressor gene that can delay aging when over expressed and accelerate aging when disrupted. Cardiovascular disease is associated with aging. For instance, the prevalence of hypertension increases with age while the level of the circulating klotho declines with age. It is not known, however, if klotho is involved in the maintenance of blood pressure. Whether klotho gene deficiency causes hypertension has never been determined. Klotho is predominately expressed in the renal distal convoluted tubule (DCT) epithelial cells although it is also found in a few of other types of cells or tissues. Kidney-specific knockout of klotho gene (KL-KO) was achieved using a cadherin promoter-Cre recombinase transgene and the loxP-flanked klotho gene. Our new exciting preliminary data showed that kidney-specific conditional KL-KO impaired renal Na excretion and vascular endothelial function and increased blood pressure (BP) significantly in mice. The level of the circulating klotho protein was decreased in spontaneous hypertensive rats (SHR). The objective of the proposed research is to determine if klotho plays a role in the maintenance of BP and if klotho deficiency is involved in the pathogenesis of hypertension. This objective will be achieved by pursuing three interrelated specific aims using a combination of several novel approaches including kidney-specific conditional gene knockout, in vivo DCT- and endothelial cell-specific gene delivery, and real-time monitoring of blood pressure (telemetry). The specific aims are: (1) Determine if klotho plays a role in the maintenance of blood pressure by testing the effect of kidney-specific conditional KL-KO on Na excretion, endothelial function, and blood pressure. (2) Determine a novel role of klotho in the regulation of Na-Cl cotransporter (NCC) and Na, K-ATPase (ATPase) in the DCT cells in kidneys. (3) Determine the role of the circulating klotho in the development of spontaneous hypertension and vascular dysfunction by DCT-specific gene delivery of ADAM10, a disintegrin that cleaves and releases klotho from DCT cells. These studies will demonstrate, for the first time, important roles of klotho in the maintenance of blood pressure and in the pathogenesis of hypertension. The results will provide novel mechanism that klotho protects the cardiovascular system. Completion of the project may reveal new insights into therapeutic strategies for hypertension and related cardiovascular disorders.